A rotten-egg smell that appears only at the hot tap in Wentzville points to a different place than a smell that shows up at both taps. Before you change anything, test both taps in the same room and see which one carries the odor. This single comparison will save you time and guesswork.
Start With the Side-by-Side Test
Use two clean glasses. Run the cold tap for about a minute, then fill a glass and smell it right away. Do the same with the hot tap. Smell each glass again after it sits for a few minutes, since some odors become easier to notice as the water warms or cools. Write down which tap smells, how strong it is, and whether the smell is worst on the first draw in the morning.
- Smell the cold water from a bathroom sink and a kitchen sink.
- Smell the hot water from the same two sinks, after running each tap briefly.
- Check whether the odor fades after the hot tap has run for several minutes.
- Note whether the smell is only in the hot line, only in the cold line, or in both.
Rule Out the Drain First
A rotten-egg smell can also come from the drain rather than the water. A drain trap that has dried out lets sewer gas rise into the room. To check, pour a little water down the drain of the sink in question and let it run, then smell the drain opening itself. If the odor is strongest at the drain and not in the glass, the water is probably not the source. Drain problems usually do not change between hot and cold taps, so they are less likely to explain a hot-only odor.
What Usually Sits Behind a Hot-Only Odor
When the smell is limited to hot water, the water heater is the first place most homeowners look. Many tanks contain a metal anode rod designed to slow corrosion of the tank itself. Under some conditions, bacteria in a warm tank can produce hydrogen sulfide, the gas that gives water its rotten-egg character. Hot water is warmer, so the reaction can be more noticeable there. This is a common pattern to investigate, but it is a pattern to check, not a conclusion. A licensed plumber can inspect the tank and anode rod, and can tell you what the tank condition looks like before any work is done.
When Wentzville Public Water Is in the Mix
Public water reports for Wentzville describe very hard water and disinfection topics such as trihalomethanes and haloacetic acids. Those reports do not describe a sulfur smell as a routine concern, so a rotten-egg odor at one tap is worth treating as a separate question. If both taps smell, or if the smell comes with a change in color, cloudiness, or a new taste, contact your water provider and ask whether anything changed in the supply that week. Keep your side-by-side notes so you can describe the pattern clearly.
If You Are on a Private Well
Private wells in the area include river-bottom alluvial wells and deep bedrock wells, and some of them carry sulfur-related odors, along with iron, manganese, and hardness. Private wells are not covered by a public water report, so you need your own lab results. Ask the lab for a hydrogen sulfide test on the cold water, since a general bacteria test will not answer that question. A sulfide result tells you what is in the water. It does not tell you why the hot line is worse, so pair it with the hot-versus-cold comparison above.
A Practical Order of Steps
- Smell both taps and log which one carries the odor.
- Check the nearby drains for a dry trap and rule out sewer gas.
- Ask a licensed plumber to inspect the water heater, including the anode rod and tank.
- If you are on a private well, send cold water for a sulfide test and a bacteria test.
- Recheck the hot and cold taps after any repair or treatment change, and compare the results with your log.
A hot-only smell is not a reason to panic, but it is a reason to test methodically. A clear log, a drain check, and a look at the water heater will tell you more than guessing at the cause.